This invention provides hybrid polymerizable compositions useful for a wide range of applications. The compositions are particularly useful in the dental field, where such compositions can be used in the formation and construction of artificial teeth, enamel layers, denture bases, denture baseplates, denture liners, denture repair, splints, orthodontic appliances, custom trays, veneers, crowns and bridges, repairs for natural teeth, restorations, fillings, and the like. More specifically, the invention relates to polymeric compositions comprising cross-linked polymers, ground highly cross-linked polymers, monomers, and multifunctional crosslinking monomers or oligomers for said monomers, and optionally uncross-linked polymers which form precursor blends. These precursor blends are capable of being formed or molded and polymerized to provide articles possessing superior wear resistance, physical and physiochemical properties. Furthermore, the compositions have excellent molding properties and processing capabilities useful in the production of artificial teeth, dental crowns, or other dental restorations. This invention also includes the artificial teeth and other restorations produced from such materials.
Artificial teeth should exhibit certain desirable physical characteristics to be suitable for use and offer desirable benefits to patients. For example, they should be hard for effective chewing and resistant to abrasion and chipping during use. They also should be durable and stable to solvents, foods, water, cold and hot and maintain esthetics without discoloration. In addition, they should have good esthetics to mimic natural dentition with esthetically acceptable color, i.e., close to that of natural teeth. The teeth should not cause excessive wear to opposing natural or artificial teeth, crowns or bridges, should not wear or deform out of occlusion, and should be capable of being bonded firmly to supportive structures. They should also be adjustable to ordinary means of physical shaping, grinding, and polishing.
Typically, artificial denture teeth are either methacrylate-based plastic teeth or ceramics-based porcelain teeth. In general, artificial plastic teeth are made from PMMA and modified PMMA polymers and MMA and modified MMA liquids. Some composite based teeth are also available in the market. Recently, plastic teeth have largely eliminated porcelain teeth from the denture tooth market due to various advantages, such as better bond to the denture base, lighter weight, toughness, less undesirable noises during chewing, and less wear, to the opposing natural or artificial teeth, crown, or bridge. However, plastic teeth have the disadvantage of being more subject to wear than porcelain teeth. Of the presently available organic compositions used for the construction of artificial teeth, most are composed of acrylics, often cross-linked by polyfunctional moieties. While such compositions are commonly used for artificial teeth, they nonetheless possess certain drawbacks. In general, artificial teeth made of currently available acrylic compositions do not have sufficient wear resistance and can be deformed by relatively low biting forces. The deficiency in wear resistance and limited loading capability of current polymeric artificial teeth are apparent when they are compared to natural or ceramic teeth, crowns or bridges. In addition, the use of implant therapy and over dentures becomes more popular, where highly wear resistant artificial teeth are imperative. Thus, there is a need for artificial teeth having better wear resistance, durability and load-bearing capability.
The patent literature disclose various dental compositions made with higher cross-linked polymers and prepolymers, and composites incorporated with inorganic particles in the polymer matrix.
For example, Erdrich et al., U.S. Pat. No. 7,368,486 discloses dental compositions for making artificial teeth and/or their enamel or cutting area. The dental composition comprises MMA, crosslinked PMMA, splinter polymer, and a methacrylate-based pearl polymer, in which inorganic dental glass is polymerized as filler, Rosenfeld, U.S. Pat. No. 7,189,076 discloses a method of making an artificial tooth for a denture and the tooth so made, the method including making a form tooth of a plastic tooth or an existing denture tooth, using the form tooth to make a mold form, placing a thin layer of polycarbonate incisal material in the bottom of the mold form and conforming the material to the mold form, subjecting the layer of incisal and body material to a vacuum and then to a curing light in an oxygen-free atmosphere, adding additional layers of approximately 2 mm of the incisal and body material and exposing each layer to a vacuum and light curing step until the mold form is full. The tooth is then removed from the mold form and again exposed to a vacuum and light curing step.
Liu, U.S. Pat. No. 6,384,107 discloses dental compositions, products, and processes using silicon containing abrasion resistant material. The produced dental products are abrasion-resistant and self-lubricating across their entire cross sections. Dental compositions useful for forming dental products in accordance with the invention preferably include an ethylenically unsaturated silane. The composition is formed into a dental prosthesis such as an artificial tooth, inlay, onlay, facing, crown or bridge.
Oswald et al., EP 1,264,581 discloses a synthetic material tooth which is built up from a photopolymerizable incisor material, a photopolymerizable dentin material and, optionally, at least one other photopolymerizable material in successive intensively bonded together layers, characterized in that injection-molded or cast nipples are provided at the boundary surfaces of the layers.
Deguchi et al., U.S. Pat. No. 6,063,830 provides a dental curable composition wherein an inorganic filler treated with a silane compound is uniformly dispersed in a fine state in urethane (meth)acrylate, thereby imparting strong toughness, wear resistance, transparency and moldability to an artificial tooth. The colloidal silica has an average primary particle size of from 1 to 85 nm, with at least one silane specific compound.
Nagel et al., EP 0,677,286 discloses artificial teeth containing polymethacrylate, barium aluminium silicate glass and microfine silica, characterized in that it essentially consists of 15-35% by weight of polymethacrylate, 35-75% by weight of barium aluminium silicate glass having a mean particle size of 0.1-5 micrometers, and 5-25% by weight of silica having a mean particle size of 0.01-0.2 micrometer.
Tateosian et al., U.S. Pat. No. 4,698,373 discloses compositions that are hardenable by exposure to heat or electromagnetic radiation by dissolving them together to form a blend form about 0% to about 50% by weight of an uncross-linked polymer, from about 2% to about 30% of a polymerizable monomer, from about 10% to about 70% of a cross-linked polymer in the form of discrete particles having average diameters of from 0.001 micron to about 500 microns and being swollen in said solution and from about 20% to about 70% of a crosslinking agent for said monomer.
Roemer et al., U.S. Pat. Nos. 4,396,476 and 4,396,377 disclose compositions hardenable by exposure to heat or electromagnetic radiation by blending form about 0% to about 50% by weight of an uncross-linked polymer, from about 20% to about 66% of a polymerizable monomer capable of dissolving said polymer, from about 10% to about 70% of a cross-linked polymer in the form of discrete particles having average diameters of from 0.001 micron to about 500 microns and being swollen in said monomer, and from about 0.25% to about 27% of a cross-linking agent for said monomer.
Although some artificial teeth materials described in the patent literature have some desirable properties, there is a need for developing new tooth materials with improved wear resistance and esthetics that are easy to manufacture. In general, artificial teeth made from the combination of composite and acrylic compositions are not easy to manufacture and the use of inorganic fillers in composite can potentially abrade the tooth molds. Artificial teeth made of currently available acrylic compositions incorporating cross-linked polymers and cross-linking agents tend to not provide sufficient wear resistance.
One object of this invention is to provide compositions which are useful in the construction of artificial teeth and their enamel layers along with other dental appliances. The compositions of this invention lead to products having improved wear resistance and superior physical and esthetic characteristics.